1. Field of the Invention
Embodiments of the present disclosure relate to light source driving devices, and particularly to a light source driving device integrated with an alternating current (AC)/direct current (DC) converter.
2. Description of Related Art
Conventionally, discharge lamps, such as Cold Cathode Fluorescent Lamps (CCFLs) and External Electrode Fluorescent Lamps (EEFLs) have been used as light sources for liquid crystal displays (LCDs). In LCD modules, current through the lamps is controlled by adjustment of a duty cycle of Pulse-Width Modulator (PWM) controller.
FIG. 6 shows one such light source driving device to drive a light source module 14. The light source driving device comprises an AC power source 10, an AC/DC converter 11, an inverter circuit 12, a PWM dimming controller 13, a PWM dimming isolator 131, and a PWM dimming driving circuit 132. The AC/DC converter 11 comprises a Power Factor Correction (PFC) circuit 110, a DC/AC converting circuit 111 and an isolating and rectifying circuit 112.
The AC power source 10 provides an electrical signal, which is converted to a DC signal via the PFC circuit 110, and output to the DC/AC converting circuit 111. The DC/AC converting circuit 111 converts the DC signal to a square-wave signal isolated by the isolating and rectifying circuit 112. The isolating and rectifying circuit 112 converts the isolated square-wave signal to another DC signal. The inverter circuit 12 converts the received DC signal to a sine-wave signal, which is output to the light source module 14. The PWM dimming controller 13 outputs a control signal to control output of the DC/AC converting circuit 111 according to a current feedback signal output from the light source module 14 via the PWM dimming isolator 131 and the PWM dimming driving circuit 132.
Current through the light source module 14 is adjusted by adjusting the duty cycle of the control signal output from the PWM dimming controller 13. In this way, components of the DC/AC converting circuit 111 are switched frequently, which accelerates aging and shortens life of the components. In addition, there is need for a current feedback circuit in the light source driving device, which increases cost and unit size.